Characterization of a modular microfluidic photoionization detector

International audiencePhotoionization detectors with a small ionization chamber can contribute to overall gas analyserminiaturization. This work reports the characterization of a microfluidic photoionization detectorprototype (μPID) which is constructed to be modular for easy replacement of the components andmaintenance. The device is fabricated by micromilling and electrical discharge machining, dispensingclean room fabrication techniques. The μPID ionization chamber is a microchannel and four channeldesigns are presented and tested in experiments in order to evaluate the influence of the geometricalparameters on the detector performance. The chamber volumes of the channel designs range from 1.1to 6.7 μL. Experimental characterization of the prototype is performed when it is used without and witha portable gas chromatograph (GC) for volatile organic compounds (VOCs) analysis. When a sampleof 100 ppm toluene is injected directly into the μPID, it can generate a current signal up to ~4 nA. Whenused without a GC, the device showed a linear response for an injection of toluene gas concentrationsranging from 1 to 100 ppm. A combination of high illumination area and electrode area resulted in thehighest signal in the μPID with a detection limit of ~40 ppb of toluene. When integrated to the portableGC, the detection limit reached for toluene is ~140 ppb. The detection limit for toluene was furtherreduced to low ppb levels (~5 ppb) when a preconcentrator was integrated into the sampling loop of theportable GC